A light touch is the last phrase one would use to describe Sadie Jones’s approach to writing fiction — until now. Her previous novels, “The Outcast” and “Small Wars,” were tense knots of strangled emotion, set within enclaves of strictly regulated 1950s British society. While they were no picnic, they were nonetheless very good books in their grimly discomfiting way, distinguished by clear language and brutal candor.

With “The Uninvited Guests,” her third novel, Jones has set out to create a work with a dramatically different tone.

Lightness — by which I mean the sly, subversive dexterity of a Mozart opera or Shakespeare’s “A Midsummer Night’s Dream” — is the elusive quality that Jones’s enchanted new novel reaches for, and lightness is what it achieves.

She sets the scene this time in Downton Abbey territory, in a manor house somewhere not far from Manchester, on the last day of April 1912.

The estate, called Sterne, is the much-loved home of the Torrington-Swifts, who are deep in preparation for a dinner party to celebrate the 20th birthday of Emerald, the family’s middle child.

Jones luxuriates in describing these preparations, and readers can’t help reveling in the voluptuous way she serves up details. Glistening with hyper-reality, her still lifes in prose contribute to a hallucinatory mood, so that as the story unfolds, it begins to seem like a seductive dream about a familiar place.

Lest we sink too comfortably into this pleasurable Edwardian reverie, Jones takes care early in the narrative to display the cracks in the red-brick solidity of Sterne. She is quick to point out that the Torrington-Swifts have only a fragile hold on their cherished estate, which they bought when Emerald was a baby. Sterne is now groaning under piles of debt and, to the family’s great distress, might soon be put on the auction block.

What happens next will show how lightly we perch on what feels like solid ground. When the guests arrive for the birthday dinner, they bring upsetting news: A dreadful train accident has occurred nearby, and while nobody can agree on exactly what happened, the Great Central Railway has decreed that Sterne must take in the survivors. Soon, to the distracted annoyance of the Torrington-Swifts and their guests, a drab little gaggle of third-class passengers emerges onto the drive and is promptly deposited in the morning room so that the family can get on with its dinner.

With infinite control, Jones proceeds from here to overturn every careful refinement in the house.

The mock turtle soup ends up, disastrously, all over the kitchen floor. An epic thunderstorm, thick with electricity, begins to pound the windowpanes. Telephone calls to the railway remain unanswered. The passengers object to being shut up in the morning room and, complaining of hunger, begin to wander about the house — and why does it seem that there are suddenly more of them, and will they steal the silver? Who is the dubious gentleman who shows up claiming to be a survivor from first class, and what is his shadowy relationship to Mrs. Torrington-Swift?

In the end, as if the house were spellbound, everything that seemed permanent becomes uprooted, subverted, changed.

There’s a pony in the youngest child’s bedroom and cartloads of mud from the garden on the stairs. Children take on the role of grown-ups, and adults act like children. The high and mighty are brought low, while the lowly become exalted.

As Sterne undergoes these transformations, the narrative keeps shifting as well, morphing from a country-house comedy to a locked-house mystery, a fairy tale, a ghost story with horror-movie elements, and an unexpectedly moving parable about hospitality. Intentionally stylized, it’s forever calling attention to its theatricality, referring to Sterne variously as a stage set, ballet or series of paintings. It also calls to mind a thousand other books, and that, too, is intentional.

Jones’s point is to remind us how porous the barrier is between all distinctions, in art as well as in society. Whatever our station, we are all the uninvited guests in this life, she’s telling us, with a duty to treat others as we would ourselves. She manages to make these old truths seem new and does so with the haunting lightness of a dream.